In my Pat. No. 3,768,705 there is described a pliant, elastic container for toothpaste, cream, or other fluent materials, which has a forward outlet or discharge portion and a one-way follower or piston in the container. The follower is disposed at the rear of the fluent material and sealingly engages the container wall, and is automatically moved by ambient air pressure toward the outlet after each dispensing of the material. The follower is arranged to grip and latch onto the container wall to prevent its movement way from the outlet of the container. Dispensing of the material occurs as a result of squeezing or deflecting the container at any point, including the region forwardly of the follower, directly at the location of the follower, the region rearwardly of the follower, and at the discharge portion of the container.
My Pat. No. 3,870,200 discloses a similar dispenser of fluent materials but does not rely upon the squeezing of the pliant walls of the container to discharge the fluent material as provided by Pat. No. 3,768,705. Rather, it utilizes a hollow head or dome of pliant, elastic material which is positioned at the end of the container opposite from its one-way follower and which incorporates a central discharge nozzle. A deforming force exerted on the hollow head or dome discharges the fluent material through the nozzle. Release of the deforming force on the head or dome, or other parts of the container, and the return of the head or other container part to its initial shape has the effect of producing a subatmospheric pressure or vacuum within the container in advance of the one-way follower or piston, and enables the follower to move towards the discharge nozzle.
In Pat. No. 3,870,200 the follower or piston includes a main body having a central hub and an outer rim, with intervening stiffener ribs interconnecting the two parts for relative rigidity.
In both Pat. Nos. 3,768,705 and 3,870,200 the sealing of the follower with the container wall is provided by a pair of grip seals. One seal points toward the outlet of the container and prevents material from being forced out of the rear of the container when the container is squeezed. The other seal points toward the rear of the container and prevents air from entering the container after the container has been squeezed.
The dispensers described in Pat. Nos. 3,768,705 and 3,870,200 work well. However, if the container in either dispenser were squeezed with excessive force, the seals would lose their ability to seal and, therefore, material would be extruded rearwardly out of the container or air would be sucked into the container. Specifically, there are two circular sealing contacts between the lips of the two seals and the inner surface of the container before the container is squeezed. Analysis indicates that, under excessive force, the sealing between the lips and the container's inner surface portion will not maintain congruency because the lips are inadequately supported, and the sealing will fail. Although Pat. No. 3,870,200 discloses intervening stiffener ribs, these ribs do not provide the necessary support to prevent such sealing failure.